JP2006109670A - Three-phase missing phase detection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-phase missing phase detection circuit capable of protection control of three-phase load by positively performing missing phase detection in a three-phase AC power supply. <P>SOLUTION: This detection circuit includes an R-phase current detection circuit for detecting an R phase; an S-phase current detection circuit 5 for detecting an S-phase current; an R-phase current value rectifier/smoother and an S-phase current value rectifier/smoother for rectifying and smoothing respective outputs; and a phase comparator 8 for comparing phases of respective outputs. If it is detected that an output of at least one of the rectifiers/smoothers is below its predetermined value or an output of the phase comparator 8 is at a 180-degree phase, it is determined as missing phase, so that enegization into a three-phase load 3 is shut down by a switch 2 to protect an apparatus. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a three-phase open phase detection circuit for detecting a phase loss of a three-phase AC power source and protecting the device in a device using a three-phase AC power source as a power source.

  Conventionally, this type of three-phase phase loss detection circuit detects the voltage between each phase and neutral phase of a three-phase AC power source, and determines the phase loss based on the phase of each phase. 1).

  FIG. 5 shows a conventional three-phase phase loss detection circuit described in Patent Document 1, and FIG. 6 shows its signal waveform. As shown in FIG. 5, as means for detecting the voltage between each phase of the three-phase AC power supply 1 and the neutral phase, a phase detection circuit 10 using a photocoupler 101 and each phase output from the phase detection circuit 10 It is comprised from the control part 9 which determines a missing phase based on a signal.

In this configuration, when the signal between each phase and the neutral phase detected by the phase detection circuit 10 is normal, the phase difference between each phase is t1 as shown in FIG. The control unit 9 determines that the phase difference t1 is normal if the phase difference t1 is within a predetermined range, and the phase is missing if the phase difference t1 is not within the predetermined range.
JP-A-8-126194

  However, in the conventional configuration, when the three-phase load 3 has a neutral point 31 like an electric motor, an open phase occurs in, for example, the R phase of the three-phase AC power source 1 while the three-phase load 3 is energized. Then, an R-phase load terminal voltage having the same potential as the neutral point 31 is generated at the R-phase load terminal 32 of the three-phase load 3 and applied to the photocoupler 101 disposed between the R-phase and N.

  The R-phase load terminal voltage applied to the photocoupler 101 is approximately a half of the power supply voltage, but when the three-phase AC power supply 1 is intended to correspond to a wide range of power supply voltages, for example, rated ± 15%, Considering the component variation, the photocoupler 101 is erroneously detected, and a detection signal similar to that shown in FIG. 6 is input to the control unit 9 and the control unit 9 determines that the phase is normal, and phase loss detection cannot be performed. It was.

  In addition, it is necessary to add a dedicated circuit for three-phase phase loss detection, and in order to detect the power supply voltage, a problem that requires an insulation distance and a large mounting area in the circuit mounting design, and There was a problem of cost increase.

  The present invention solves the above-described conventional problems. Even when a phase failure of a three-phase AC power source occurs due to disconnection of a wire or disconnection of a connection line during energization of a three-phase load, the present invention can be detected without erroneous detection. The purpose is to ensure phase detection and protect the equipment.

  Another object of the present invention is to reduce the influence on the mounting area and reduce the cost increase.

In order to solve the conventional problems, a three-phase open phase detection circuit according to the present invention includes a three-phase AC power source, a three-phase load connected to the three-phase AC power source via a switch, and the switch A first current detection circuit that detects a first phase current of the three-phase AC power supply, and a second phase current of the three-phase AC power supply; A second current detection circuit is provided, and a rectifying / smoothing means for rectifying and smoothing each output and a phase comparing means for comparing the phases of the respective outputs are provided, and the control unit outputs a predetermined output from at least one rectifying and smoothing means. The switch is opened when a value below the value is detected or when the output of the phase comparison means detects a phase of 180 degrees.

  The first phase and the second phase are output from the respective rectifying / smoothing means, and the third phase is the output from the first current detection circuit and the second current detection circuit by the phase comparison means. By detecting the phase difference of the three-phase load, it is possible to detect the phase failure even in the case of a phase failure while the three-phase load is energized, and the power to the three-phase load can be shut off by the switch, thus protecting the equipment. Can do.

  The three-phase phase loss detection circuit of the present invention uses a three-phase load as a compressor and the first and second current detection circuits also serve as a compressor overcurrent protection current detection circuit.

  As a result, it is not necessary to add a dedicated circuit for detecting the three-phase phase loss, and the influence on the mounting area and cost increase can be reduced.

  The three-phase phase loss detection circuit of the present invention can reliably detect phase loss during energization of a three-phase load, can be realized with a small mounting area and low cost, and can protect equipment.

  A first invention includes a three-phase AC power source, a three-phase load connected to the three-phase AC power source via a switch, and a control unit that controls opening and closing of the switch. A first current detection circuit that detects the current of the first phase of the phase AC power supply and a second current detection circuit that detects the current of the second phase of the three-phase AC power supply are provided, and each output is rectified and smoothed. A rectifying / smoothing unit that compares the phase of each output, and the control unit detects that the output of at least one rectifying / smoothing unit is a predetermined value or less, or the output of the phase comparing unit is By opening the switch when a 180-degree phase is detected, it is possible to reliably detect a phase failure even when a three-phase load is energized, and the energization of the three-phase load is interrupted by the switch. Can protect the equipment.

  In particular, the second aspect of the present invention uses a three-phase load according to the first aspect of the present invention as a compressor, and the first and second current detection circuits also serve as a current detection circuit for overcurrent protection of the compressor. There is no need to add a dedicated circuit for phase detection, and the effect on mounting area and cost increase can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a circuit diagram of a three-phase phase loss detection circuit according to the first embodiment of the present invention. In FIG. 1, a three-phase AC power source 1 is connected to a compressor 3 that is a three-phase load via a switch 2. R-phase current detection circuit 4 for detecting the current of two phases (R-phase, S-phase) of each phase (R-phase, S-phase, T-phase) from the three-phase AC power source 1 to the compressor 3; S-phase current A detection circuit 5 is provided, and each output is connected to R-phase current value rectifying and smoothing means 6 and S-phase current value rectifying and smoothing means 7 for rectifying and smoothing, and also connected to phase comparing means 8 for comparing the respective phases. Has been. The outputs of the R-phase current value rectifying / smoothing means 6, the S-phase current value rectifying / smoothing means 7, and the phase comparison means 8 are input to the control unit 9, and the control unit 9 controls the switch 2 according to those inputs. It is configured.

  The operation and action of the three-phase phase loss detection circuit configured as described above will be described below.

  First, the operation when there is no phase loss will be described. The current flowing through the compressor 3 is detected by the R-phase current detection circuit 4 and the S-phase current detection circuit 5, and the output waveform thereof is an AC voltage waveform whose phase is shifted by 120 degrees as in R1 and S1 of FIG. R1 is rectified and smoothed by the R-phase current value rectifying and smoothing means 6 and S1 is rectified and smoothed by the S-phase current value rectifying and smoothing means 7 to obtain DC voltage waveforms of R2 and S2. The outputs R1 and S1 of the R-phase current detection circuit 4 and the S-phase current detection circuit 5 are also input to the phase comparison means 8 at the same time. The phase comparison means 8 determines whether or not the phase difference between R1 and S1 is 180 degrees and outputs an output waveform P2. For example, if the phase difference is 180 degrees, P2 is a Lo output, and otherwise P2 is a Hi output. In this case, the phase difference is 120 degrees, resulting in a Hi output.

  The control unit 9 determines the magnitudes of the outputs R2 and S2 of the R-phase current value rectifying and smoothing means 6 and the S-phase current value rectifying and smoothing means 7, and one of the outputs is equal to or greater than the first set value (A1) and the second set value. (A2) In the following cases, it is determined to be normal, and the switch 2 is controlled to be closed. When it is equal to or greater than the second set value (A2), it is determined to be an overcurrent, and the switch 2 is controlled to open. For example, when the current of the compressor 3 becomes too large due to an abnormality in the refrigeration cycle of the air conditioner and exceeds the second set value (A2), the energization to the switch 2 is stopped and the switch 2 is controlled to be opened. 3 is stopped and protection control is performed. When there is no phase loss and no overcurrent as shown in FIG. 2, protection control is not performed. Further, the control unit 9 controls the opening of the switch 2 to stop the energization to the compressor 3 by the output P2 from the phase comparison unit 8 and stops the energization to the compressor 3, but protects because the P2 is a Hi output. There is no control.

  Next, a case where an open phase occurs in the R phase will be described. When the R phase is lost, the R phase current becomes zero. Therefore, as shown in FIG. 3, the output waveform R1 of the R phase current detection circuit 4 becomes zero, and the output R2 of the R phase current value rectifying and smoothing means 6 is also zero. become. The output P2 of the phase comparison means 8 is a Hi output because the phase difference between R1 and S1 is not 180 degrees.

  The control unit 9 does not perform protection control by the phase comparison unit 8 because the output P2 from the phase comparison unit 8 is a Hi output, but the output R2 of the R-phase current value rectifying and smoothing unit 6 is not more than the first set value (A1). Therefore, it is determined that the R phase is open, and the switch 2 is controlled to open, the energization to the compressor 3 is stopped, and open phase protection control is performed.

  Even when the S phase is lost, the control unit 9 detects the zero voltage of the output S2 of the S phase current value rectifying and smoothing means 7 as in the case of the R phase, and determines that the S phase is lost. 2 is controlled to open, and the power supply to the compressor 3 is stopped to perform phase loss protection control.

  On the other hand, when an open phase occurs in the T phase, the compressor 3 is driven by two phases of the R phase and the S phase, so that the single phase operation is performed. Therefore, the output waveforms detected by the R-phase current detection circuit 4 and the S-phase current detection circuit 5 are AC voltage waveforms whose phases are shifted by 180 degrees as in R1 and S1 of FIG. The output waveforms of the R-phase current value rectifying and smoothing means 6 and the S-phase current value rectifying and smoothing means 7 are R2 and S2. The phase comparison means 8 determines the phase difference between R1 and S1, and since the phase difference is 180 degrees, the output waveform P2 becomes Lo output.

  The control unit 9 indicates that the output waveforms of the R-phase current value rectifying / smoothing means 6 and the S-phase current value rectifying / smoothing means 7 are normal when R2 and S2 are not less than the first set value (A1) and not more than the second set value (A2). However, since the output P2 from the phase comparison means 8 is Lo output, the switch 2 is controlled to open, the energization to the compressor 3 is stopped, and phase loss protection control is performed.

As described above, in this embodiment, the R phase current detection circuit for detecting the R phase current and the S phase current detection circuit for detecting the S phase current are provided, and the rectifying and smoothing means for rectifying and smoothing the respective outputs. And a phase comparison means for comparing the phases of the respective outputs, and when the output of the rectifying and smoothing means of either the R phase or the S phase is detected to be a predetermined value or less, or the output of the phase comparison means is 180 degrees phase When phase loss is detected, phase loss protection control is performed, and power to the compressor can be shut off by a switch, thus protecting the equipment.

  In addition, by combining the R-phase and S-phase current detection circuits with the current detection circuit for overcurrent protection of the compressor, there is no need to add a dedicated circuit for detecting the three-phase phase loss, and this has an effect on the mounting area. Cost increase can be reduced.

  As described above, the three-phase phase loss detection circuit of the air conditioner according to the present invention can realize the phase loss detection while energizing the three-phase load reliably, with a small mounting area and at a low cost, and can protect the equipment. Therefore, it can also be applied to the protection of equipment by detecting phase loss such as inverter equipment using a three-phase AC power supply as a power source.

Circuit diagram of a three-phase phase loss detection circuit according to Embodiment 1 of the present invention Output waveform diagram of each part at normal time in Embodiment 1 of the present invention Each part output waveform diagram at the time of R-phase phase loss in Embodiment 1 of the present invention Each part output waveform diagram at the time of T-phase loss in Embodiment 1 of the present invention Circuit diagram of conventional three-phase phase loss detection circuit Waveform diagram showing the input signal to the conventional control unit

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Three-phase alternating current power supply 2 Switch 3 Three-phase load 4 R phase current detection circuit 5 S phase current detection circuit 6 R phase current value rectification smoothing circuit 7 S phase current value rectification smoothing circuit 8 Phase comparison means 9 Control part

Claims (2)

A three-phase AC power source, a three-phase load connected to the three-phase AC power source via a switch, and a controller for controlling the opening and closing of the switch; A rectifying / smoothing means for providing a first current detecting circuit for detecting a current of a phase and a second current detecting circuit for detecting a current of a second phase of a three-phase AC power supply, and rectifying and smoothing each output; Phase comparison means for comparing the phases of the respective outputs is provided, and the control unit detects that the output of at least one rectifying / smoothing means is a predetermined value or less, or the output of the phase comparison means detects a phase of 180 degrees. A three-phase phase loss detection circuit that opens the switch. 2. The three-phase open phase detection circuit according to claim 1, wherein the three-phase load is a compressor, and the first and second current detection circuits are also used as a current detection circuit for overcurrent protection of the compressor. Air conditioner.

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